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Record-Breaking Heat

Published: July 6th, 2010

Last updated: August 17, 2010

The intense heat wave that is gripping the crowded metropolitan corridor and toppling records from Washington, DC to Boston, with temperatures hovering near or just above 100 degrees Fahrenheit during the first full week of July, is raising questions about whether events like this are likely to become more common and/or severe as the climate warms in response to greenhouse gas emissions.

The short answer: yes and yes, but with an important caveat. No individual extreme weather event — including this heat wave — can be caused by climate change. Rather, what climate change does is shift the odds in favor of certain events.

Extreme weather and climate events can cause significant damages, and heat waves are considered public health emergencies. According to the Centers for Disease Control, heat is the number one weather-related killer in the US. Hot temperatures contribute to increased emergency room visits and hospital admissions for cardiovascular disease, and can cause heat stroke and other life-threatening conditions.

Events such as the Chicago heat wave of 1995 and the 2003 European heat wave, which killed an estimated 40,000 people, have proven especially deadly to vulnerable populations, such as the elderly and persons with respiratory illnesses (See "Report on Excess Mortality in Europe During Summer 2003"). Other societal impacts of extreme heat include livestock mortality, increases in peak energy demand, crop damage, and increased demand for water, as detailed in a report of the US Global Change Research Program.

Climate Central has analyzed projected midcentury August temperatures for a list of 21 major American cities, under a fairly conservative warming scenario, and found that some startling changes may lie ahead.

Today, the only cities on the list where more than half the days in an average August exceed 95°F are Phoenix and Dallas; by the 2050’s, Houston, Sacramento, Tampa Bay and Orlando could join them. Today, seven cities break 90°F on at least half of the days of a typical August; by the 2050’s, they could be joined by Atlanta, Denver, Indianapolis, Miami, and Philadelphia. And, by midcentury, a dozen cities could average more than one day over 100°F per August, where today only three share that dubious distinction.

The summer of 2010 is one for the history books. June and July saw record-breaking temperatures around the globe and a number of severe weather events caught worldwide attention, including the Western Russian heat wave and the floods in Pakistan brought on by strong monsoon rainfall.

Dr. Otis Brown of the University of Miami explains the differences between climate and weather, and long-term climate changecompared to heat waves. Brown also discusses the utility of weather forecasts and climate models in today's society.

August Heat
By mid-century, a dozen cities could average more than one day over 100°F per August, where today only three share that dubious distinction.

This graphic shows the new record high temperatures for the 17 nations that have broken their national records so far in 2010. Previously, the largest number of countries to break such records in a single year was 14, according to Weather Underground and The Guardian newspaper. If verified, the record set in Pakistan would also stand as the warmest temperature ever recorded in the continent of Asia. Click on the graphic for a larger version. Graphic design by Russell Freedman.